Hydraulic camshaft adjuster

ABSTRACT

A camshaft phaser for variably adjusting the control times of gas exchange valves of an internal combustion engine, including: a stator and a rotor which can be rotated relative to the stator, wherein a plurality of hydraulic chambers are formed between the stator and the that are separated by radially inwardly projecting webs of the stator. Radially outwardly projecting vanes are formed on the rotor that divide each of the hydraulic chambers into first and second groups of working chambers with an opposing effective direction. A pressure medium pump is adapted to apply a pressure medium to the working chambers. A central valve controls the oil pressure in the working chambers. The pressure medium pump is directly connected to the working chambers in each ease via a pressure medium channel; the central valve is connected to the working chambers via discharge channels; and the central valve exclusively controls the pressure medium discharge from the working chambers.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is the U.S. National Phase of PCT Appln. No. PCT/DE2019/100822, filed Sep. 18, 2019, which claims priority to DE 102018127733.4, filed Nov. 7, 2018, the entire disclosures of which are incorporated by reference herein.

TECHNICAL FIELD

The disclosure relates to a hydraulic camshaft phaser.

BACKGROUND

Hydraulic camshaft phasers are used in internal combustion engines to adapt a load condition of the internal combustion engine and thus to increase the efficiency of the internal combustion engine. Hydraulic camshaft phasers that work according to the vane principle are known from the prior art. In their basic structure, these camshaft phasers generally have a stator that can be driven by a crankshaft of an internal combustion engine and a rotor that is connected to the camshaft of the internal combustion engine for conjoint rotation. An annular space is provided between the stator and the rotor, which is divided into a plurality of working chambers by radially inwardly protruding projections connected to the stator for conjoint rotation, each of which is divided into two pressure chambers by a vane radially outwardly projecting from the rotor. Depending on the application of a hydraulic pressure medium to the pressure chambers, the position of the rotor in relation to the stator and thus also the position of the camshaft in relation to the crankshaft can be adjusted in the “early” or “late” direction. Hydraulic camshaft phasers with a central locking system are known, in which the rotor can be locked in a central position in addition to the respective end positions, in order, in particular, to facilitate an engine start. In addition, hydraulic camshaft phasers are known which, as so-called “smart phasers”, have a reservoir for the hydraulic oil.

DE 10 2012 201 558 A1 discloses a hydraulic camshaft phaser comprising a stator, a rotor arranged concentrically to the stator and rotatable about a common axis of rotation relative to the stator, and one or more volume accumulators for receiving a hydraulic fluid for hydraulic actuation of the camshaft phaser, wherein the volume reservoir(s) has an outlet in the direction of the axis of rotation.

DE 10 2006 012 733 A1 discloses a hydraulic circuit for a hydraulic camshaft phaser with a switching valve, in which, in addition to pressurizing the working chambers, an additional force from the alternating torques of the camshaft is used to rotate the rotor of the hydraulic camshaft phaser with respect to the stator.

From EP 1 221 540 A2 a hydraulic camshaft phaser for adjusting the control times of gas exchange valves of an internal combustion engine is known, in which the alternating torques of the camshaft and the hydraulic oil pressure in the working chambers are used to rotate the rotor relative to the stator.

However, the construction of the camshaft phaser known from the prior art is relatively complex due to the large number of control channels and is associated with correspondingly high production costs. In addition, such camshaft phasers have already been optimized as far as possible in terms of production technology, so that the manufacturing costs can only be reduced insignificantly with the known design.

SUMMARY

The object of the disclosure is to propose a hydraulic camshaft phaser which does not have any functional disadvantages in the known solutions, but is less complex and can be manufactured more cost-effectively.

According to the disclosure, this object is achieved by a hydraulic camshaft phaser for variably adjusting the control times of gas exchange valves of an internal combustion engine, comprising a stator and a rotor which can be rotated relative to the stator, wherein a plurality of hydraulic chambers are formed between the stator and the rotor, said chambers being separated by radially inwardly projecting vanes of the stator, wherein radially outwardly projecting vanes are formed on the rotor, said vanes dividing each of the hydraulic chambers into a first group of working chambers and a second group of working chambers with an opposing effective direction; a pressure medium pump using which a pressure medium can be applied to the working chambers; and a central valve for controlling the oil pressure in the working chambers. It is provided that the pressure medium pump is directly connected to the working chambers in each ease via a pressure medium channel; the central valve is connected to the working chambers via discharge channels; and the central valve exclusively controls the pressure medium discharge from the working chambers. With a direct supply of pressure medium to the working chamber via the pressure medium pump, large flow cross-sections can be realized in the pressure medium channels, whereby the adjustment speed of the hydraulic camshaft phaser can be improved. In addition, due to the larger flow cross-sections in the pressure medium channels, greater adjustment stability of the hydraulic camshaft phaser can be achieved, since the intake does not take place via the central valve. A simple central valve can be used, which reduces the complexity of the central valve. In addition, the central valve can be shortened, thus reducing the production costs for the central valve.

Due to the use of one or more of the measures listed below and in the claims, advantageous further developments and improvements of the hydraulic camshaft phaser are possible.

In a preferred embodiment of the disclosure, it is provided that a first check valve is arranged in a first pressure medium channel, which connects the pressure medium pump to the first working chamber of the hydraulic camshaft phaser, and a second check valve is arranged in a second pressure medium channel, which connects the pressure medium pump to the second working chamber of the hydraulic camshaft phaser. The check valves can improve the pressure regulation in the working chambers and, in particular, prevent an undesired discharge of pressure medium from the working chambers.

According to an advantageous development it is provided that the check valves are arranged or formed in a check valve plate of the hydraulic camshaft phaser. By means of a check valve plate, the check valves can be integrated particularly easily and inexpensively into the pressure medium inlet to the working chambers of the hydraulic camshaft phaser. The check valve plate can be produced simply and inexpensively as a stamped part in order to further reduce the costs for the hydraulic camshaft phaser.

In an advantageous embodiment of the hydraulic camshaft phaser, it is provided that the pressure medium channels are formed at least in sections in the check valve plate. By integrating the oil supply channels in the check valve plate, the supply of pressure medium to the working chambers of the hydraulic camshaft phaser can be controlled in a simple manner. In this way, pressure pulsations, which can impair the function of the hydraulic camshaft phaser, can be avoided.

In a preferred embodiment of the hydraulic camshaft phaser, it is provided that a check valve is arranged in the pressure medium channels for each of the first working chambers and for each of the second working chambers. The intake of pressure medium into each of the first pressure chambers and each of the second pressure chambers can be controlled by a corresponding plurality of check valves, whereby the pressure pulsations can be further reduced.

In an advantageous embodiment of the disclosure it is provided that the hydraulic camshaft phaser has a drive wheel with drive toothing, the pressure medium channels running at least in sections in the drive wheel. The drive wheel can simply be hydraulically connected to the oil supply from the pressure medium pump via appropriate supply bores. As a result, the oil supply channels can be made comparatively short, as a result of which the adjustment times of the hydraulic camshaft phaser are improved and the pressure medium requirement is lower overall.

It is particularly preferred if the drive wheel is produced as a sintered component. By means of a sintering process, the pressure medium channels can be formed in the drive wheel in a simple and cost-effective manner, wherein subsequent mechanical machining can be omitted or at least greatly reduced. As a result, the pressure medium channels can be introduced into the drive wheel essentially at no cost, which further reduces the costs for the hydraulic camshaft phaser.

An advantageous embodiment of the hydraulic camshaft phaser provides that the rotor is designed as a built rotor and has a first rotor component and a second rotor component. The two rotor components are preferably connected to one another via several pin connections. Since the rotor in the proposed hydraulic camshaft phaser can be designed without oil supply channels, the geometry of the rotor is comparatively simple and can be manufactured with comparatively little outlay on tools. A diverting sleeve is provided between the rotor and the central valve, which diverts the pressure medium discharge channels in different planes so that a simple and inexpensive slide valve can be used as the central valve.

It is particularly preferred if the rotor components are manufactured as stamped parts. A built rotor can significantly reduce the complexity for the two rotor halves, so that an inexpensive stamped part can be used instead of a comparatively expensive turned or sintered component. The production costs for the hydraulic camshaft phaser can thus be further reduced.

Alternatively, a sintered rotor can also be used, wherein the diverting sleeve between the rotor and the central valve in the case of a sintered rotor can be omitted. In a particularly preferred embodiment of the rotor, the pressure medium channels run on one of the end faces of the sintered rotor. In this way, the pressure medium channels can be introduced into the sinter blank (green compact), so that subsequent machining can be dispensed with.

In a further preferred embodiment of the hydraulic camshaft phaser, it is provided that a pressure medium path leads from the working chambers via the central valve, wherein a check valve is arranged in the pressure medium path downstream of the central valve. By means of a check valve downstream of the central valve, the pressure medium return can be connected in a simple manner to the pressure medium intake, as a result of which the oil discharged from the pressure chambers is directed back to the supply side. This can reduce the risk of air being sucked in if there is an insufficient supply. Alternatively, the check valve can also be arranged downstream of the pump intake of the pressure medium pump.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, the disclosure is explained by means of preferred embodiments with reference to the attached figures. Identical components or components with the same function are marked with the same reference symbols. In the figures:

FIG. 1 shows a first section through a hydraulic camshaft phaser according to the disclosure;

FIG. 2 shows a second section through a hydraulic camshaft phaser according to the disclosure;

FIG. 3 shows an exploded view of a hydraulic camshaft phaser according to the disclosure;

FIG. 4 shows a hydraulic circuit diagram for a hydraulic camshaft phaser according to the disclosure; and

FIG. 5 shows a further sectional illustration of a hydraulic camshaft phaser in order to visualize the pressure medium supply into the first working chamber or the pressure medium discharge from the second working chamber when the rotor is adjusted.

DETAILED DESCRIPTION

FIG. 1 shows a section through a hydraulic camshaft phaser 1 according to the disclosure for an internal combustion engine. The hydraulic camshaft phaser 1 has a stator 2 in which a rotor 3 is arranged, which can be rotated relative to the stator 2. The stator 2 has a plurality of webs 6 extending radially inward. The rotor 3 has a rotor hub 8, from which a plurality of vanes 7 protrude in the radial direction. Between the stator 2 and the rotor 3 a plurality of hydraulic working chambers 9 are formed, each of which is divided into a first working chamber 10 and a second working chamber 11 by a vane 7 of the rotor 3. In the present exemplary embodiment, a hydraulic camshaft phaser 1 with four hydraulic chambers 9 and a rotor 3 with four vanes 7 is shown, but embodiments with fewer, in particular with three hydraulic chambers, or more, in particular with five hydraulic chambers, are also possible. A chamber discharge 12 is formed on the rotor 3, via which the pressure medium, in particular the engine oil of the internal combustion engine, can flow out of the working chambers 10, 11. The hydraulic camshaft phaser 1 also has a central valve 5, via which the pressure medium discharge from the working chambers 10, 11 can be controlled. A diverting sleeve 13 is provided between the rotor 3 and the central valve 5, which accordingly diverts the pressure medium flowing out of the working chambers 10, 11. The central valve 5 can be displaced in the axial direction against the spring force of a spring 16 via an actuator 4, wherein the spring 16 is arranged in a piston 15 of the central valve 5. In a central opening of the rotor 3, a bushing 14 is used, on which the piston 15 and the guide sleeve 13 are supported. The stator 2 is connected for conjoint rotation via an intermediate plate 32 to a drive wheel 23 of the hydraulic camshaft phaser, which can be connected to the crankshaft of an internal combustion engine via a chain or a toothed belt and can be driven thereby. For this purpose, the drive wheel 23 has a drive toothing 24 on its periphery, with which a chain or a toothed belt can be positively received. A check valve plate 21 is arranged between the drive wheel 23 and the intermediate plate 32, which enables a direct pressure medium supply to the working chambers 10, 11 from a pressure medium pump 25 and prevents an undesired discharge of pressure medium from the working chambers 10, 11.

FIG. 2 shows a further section through a hydraulic camshaft phaser 1 according to the disclosure. It can be seen that the rotor 3 is connected for conjoint rotation to the camshaft 17 and the pressure medium is supplied via bores in the drive wheel 23. In this case, the oil supply 19 runs through the camshaft 17, which is at least partially designed as a hollow shaft, and through pressure medium channels in the drive wheel 23, directly to the working chambers 10, 11. The supply of pressure medium is not controlled by the central valve 5, since this only controls the pressure medium return from the working chambers 10, 11. A check valve 18 is provided in the pressure medium return downstream of the central valve 5, which makes it possible to feed the discharging pressure medium back into the pressure medium supply, provided that the pressure in the pressure medium return is higher than the pressure in the respective channel of the pressure medium supply.

In FIG. 3, a hydraulic camshaft phaser 1 according to the disclosure is shown in an exploded drawing. The hydraulic camshaft phaser 1 comprises a stator 2 and a rotor 3 received in the stator 2 and rotatable about a common axis of rotation relative to the stator. The rotor 3 comprises a first rotor component 34 and a second rotor component 35, wherein the two rotor components 34, 35 are connected to one another via pins 33 and are centered with respect to one another. A plurality of discharge channels 28, 29 are formed in the rotor 3, which connect the respective working chambers 10, 11 to the central valve 5 in such a way that the pressure medium discharge from the working chambers 10, 11 can be controlled by the central valve 5. In a central opening of the rotor 3, a guide sleeve is arranged, which deflects the returning pressure medium in such a way that the pressure medium can be returned from the central valve 5 via a check valve 18 into the area of the pressure medium supply. A plurality of hydraulic chambers 9 are formed between the stator 2 and the rotor 3, which are divided by the vanes 7 of the rotor 3 into a first working chamber 10 and a second working chamber 11 with different directions of action with regard to the adjustment of the hydraulic camshaft phaser 1. The working chambers 10, 11 are delimited in the axial direction on the side facing away from the stator 2 by an intermediate plate 32. The intermediate plate has a plurality of openings, of which exactly one opening in each case preferably opens into one of the first working chambers 10 or one of the second working chambers 11. The openings can each be closed by a check valve 30, 31 in a check valve plate 21 in order to prevent an undesired discharge of pressure medium from the first working chamber 10 or the second working chamber 11. The check valve plate 21 is clamped between the intermediate plate 32 and a drive wheel 23 of the hydraulic camshaft phaser 1, wherein the pressure medium supply channels are preferably formed in the drive wheel 23. Alternatively or additionally, the pressure medium supply channels can be formed at least in sections in the check valve plate 21.

FIG. 4 shows a hydraulic circuit diagram of a hydraulic camshaft phaser 1 according to the disclosure. The circuit diagram shown in FIG. 4 shows one of the working chamber pairs 10, 11. In this case, three or four pairs of working chambers 10, 11 are preferably provided in the hydraulic camshaft phaser 1. A pressure medium pump 25 is connected to a first working chamber 10 of the hydraulic camshaft phaser 1 via a first pressure medium supply channel 26 and to a second working chamber 11 via a second pressure medium supply channel 27.

The first working chamber 10 and the second working chamber are delimited on the stator by webs 6, not shown in FIG. 4, and are hydraulically separated from one another by a vane 7 of the rotor 7. The two working chambers 10, 11 have different directions of action with regard to the adjustment of the rotor 3. A first check valve 30 is arranged in the first pressure medium supply channel 26, which prevents discharge of pressure medium from the first working chamber 10 in the direction of the pressure medium pump 25. A second check valve 31, which prevents an undesired discharge of pressure medium from the second working chamber 11, is arranged in the second pressure medium supply channel 27. The first working chamber 10 is connected to the central valve 5 via a first discharge channel 28. The second working chamber 11 is connected to the central valve 5 via a second discharge channel 29, wherein one of the two working chambers 10, 11 may be switched to zero pressure via the position of the central valve 5. In addition, in a further switching position of the central valve 5, a discharge of pressure medium from both working chambers 10, 11 can be prevented in order to hydraulically tension the rotor 3.

In FIG. 5, a hydraulic adjustment of the rotor 3 of the hydraulic camshaft phaser 1 is shown. The camshaft change torque acts in the intended adjustment direction. The camshaft change torque presses the pressure medium from the first working chamber 10 via the rotor 3 via the open discharge channels 28 of the central valve 5 and the optional check valve 18 for connecting the pressure medium pump 25. The pressure medium is conveyed into the second working chamber 11 via the pressure medium supply channel 27, as this draws in the pressure medium. When the camshaft alternating torque acts against the adjustment direction, the check valve 31 closes and prevents rotation of the rotor 3 against the desired adjustment direction. The second working chamber 11 is acted upon with pressure medium by the pressure medium pump 25 via the pressure medium supply channel 27. The pressure medium from the first working chamber 10 can flow out via the discharge channel 28, as a result of which the volume in the first working chamber 10 is reduced and the rotor 3 is rotated in direction A. The check valve 30 in the first pressure medium supply channel 26 is closed and in this way prevents the pressure medium from flowing back in the direction of the pressure medium pump 25. The central valve 5 is in a first switching position in which the first working chamber 10 is depressurized and the discharge channel 28 is also connected to a pressure medium reservoir.

LIST OF REFERENCE SYMBOLS

1 Camshaft phaser

2 Stator

3 Rotor

4 Actuator

5 Central valve

6 Web

7 Vane

8 Rotor hub

9 Hydraulic chambers

10 First working chamber

11 Second working chamber

12 Chamber discharge

13 Diverting sleeve

14 Bushing

15 Piston

16 Spring

17 Camshaft

18 Check valve

19 Oil supply

20 Oil groove

21 Check valve plate

22 Chamber access

23 Drive wheel

24 Drive toothing

25 Pressure medium pump

26 A channel

27 B channel

28 First discharge channel

29 Second discharge channel

30 First check valve

31 Second check valve

32 Intermediate plate

33 Pins

34 First rotor component

35 Second rotor component 

1. A hydraulic camshaft phaser for variably adjusting control times of gas exchange valves of an internal combustion engine, the hydraulic camshaft phaser comprising: a stator and a rotor which is rotatable relative to the stator; a plurality of hydraulic chambers formed between the stator and the rotor; radially outwardly projecting vanes formed on the rotor, said vanes dividing each of the hydraulic chambers into a first group of working chambers and a second group of working chambers with an opposing effective direction; a central valve configured to control oil pressure in the working chambers; respective pressure medium channels configured to supply a pressure medium directly to the working chambers from a pressurized pressure medium source; the central valve is connected to the working chambers via discharge channels; and the central valve exclusively controls a pressure medium discharge from the working chambers.
 2. The hydraulic camshaft phaser according to claim 1, further comprising: a first check valve arranged in a first one of the pressure medium channels which connects a pressure medium pump acting as the pressurized pressure medium source to the first group of working chambers, and a second check valve arranged in a second one of the pressure medium channels which connects the pressure medium pump to the second group of working chambers.
 3. The hydraulic camshaft phaser according to claim 2, further comprising: a check valve plate in which the check valves are arranged or formed.
 4. The hydraulic camshaft phaser according to claim 2, wherein one of the check valves is assigned to each of the first group of working chambers and to each of the second group of working chambers in the pressure medium channels.
 5. The hydraulic camshaft phaser according to claim 1, further comprising: a drive wheel with drive toothing, and the pressure medium channels extend at least in sections in the drive wheel.
 6. The hydraulic camshaft phaser according to claim 5, wherein the drive wheel is a sintered component.
 7. The hydraulic camshaft phaser according to claim 1, wherein the rotor is a sintered component, and at least one of the pressure medium channels or the discharge channels are formed in an end face of the rotor.
 8. The hydraulic camshaft phaser according to claim 1, wherein the rotor comprises a first rotor component and a second rotor component.
 9. The hydraulic camshaft phaser according to claim 8, wherein the rotor components are stamped parts.
 10. The hydraulic camshaft phaser according to claim 1, further comprising: a pressure medium return path that leads from the working chambers via the central valve, and a check valve arranged in the pressure medium return path downstream of the central valve or downstream of a pump inlet of a pressure medium pump.
 11. A hydraulic camshaft phaser for variably adjusting control times of gas exchange valves of an internal combustion engine, the hydraulic camshaft phaser comprising: a stator; a rotor located in and rotatable relative to the stator; a plurality of hydraulic chambers formed between the stator and the rotor; radially outwardly projecting vanes formed on the rotor, said vanes dividing each of the hydraulic chambers into a first group of working chambers and a second group of working chambers that have opposing effective directions; a central valve configured to control a pressure medium pressure in the working chambers; respective first and second pressure medium channels configured to supply pressure medium directly to the first group of working chambers and the second group of working chambers from a pressurized pressure medium source; respective first and second discharge channels that connect the central valve connected to the first group of working chambers and the second group of working chambers; an actuator configured to control the central valve; and the central valve exclusively controls a pressure medium discharge via the first and second discharge channels from the working chambers.
 12. The hydraulic camshaft phaser according to claim 11, further comprising: a first check valve arranged in the first pressure medium channel which connect the pressurized pressure medium source to the first group of working chambers, and a second check valve arranged in the second pressure medium channel which connects the pressurized pressure medium source to the second group of working chambers.
 13. The hydraulic camshaft phaser according to claim 12, further comprising: a check valve plate in which the check valves are arranged or formed.
 14. The hydraulic camshaft phaser according to claim 12, wherein one of the check valves is assigned to each of the first group of working chambers and to each of the second group of working chambers in the pressure medium channels.
 15. The hydraulic camshaft phaser according to claim 11, further comprising: a drive wheel with drive toothing, and the pressure medium channels extend at least in sections in the drive wheel.
 16. The hydraulic camshaft phaser according to claim 11, wherein the drive wheel is a sintered component.
 17. The hydraulic camshaft phaser according to claim 11, wherein the rotor is a sintered component, and at least one of the pressure medium channels or the discharge channels are formed in an end face of the rotor.
 18. The hydraulic camshaft phaser according to claim 11, wherein the rotor comprises a first rotor component and a second rotor component.
 19. The hydraulic camshaft phaser according to claim 18, wherein the first and second rotor components are stamped parts.
 20. The hydraulic camshaft phaser according to claim 11, further comprising: a pressure medium return path that leads from the working chambers via the central valve; and a check valve arranged in the pressure medium return path downstream of the central valve or downstream of a pump inlet of the pressure medium source. 